Dehydration Status Aggravates Early Renal Impairment in Children: A Longitudinal Study

Dehydration is common in children for physiological and behavioral reasons. The objective of this study was to assess changes in hydration status and renal impairment across school weekdays. We conducted a longitudinal study of three repeated measures of urinalysis within one week in November 2019 in a child cohort in Beijing, China. We measured urine specific gravity (USG) to determine the dehydration status, and the concentration of β₂-microglobulin (β₂-MG) and microalbumin (MA) to assess renal function impairment among 1885 children with a mean age of 7.7 years old. The prevalence of dehydration was 61.9%, which was significantly higher in boys (64.3%). Using chi-square tests and linear mixed-effects regression models, we documented the trends of the renal indicators' change over time among different hydration statuses. Compared to Mondays, there were apparent increases of β₂-MG concentrations on Wednesdays (β = 0.029, p < 0.001) and Fridays (β = 0.035, p < 0.001) in the dehydrated group, but not in the euhydrated group. As for the MA concentrations, only the decrease on Fridays (β = -1.822, p = 0.01) was significant in the euhydrated group. An increased trend of elevated β₂-MG concentration was shown in both the euhydrated group (Z = -3.33, p < 0.001) and the dehydrated group (Z = -8.82, p < 0.001). By contrast, there was a decreased trend of elevated MA concentrations in the euhydrated group (Z = 3.59, p < 0.001) but not in the dehydrated group. A new indicator ratio, β₂-MG/MA, validated the consistent trends of renal function impairment in children with dehydration. Renal impairment trends worsened as a function of school days during the week and the dehydration status aggravated renal impairment during childhood across school weekdays, especially tubular abnormalities in children.